1. Field of the Invention
This invention relates to a method of manufacturing a powder.
2. Description of the Prior Art
A calcium phosphate-based compound, a kind of ceramic material, is widely used as, for example, a biomaterial and a stationary phase material for chromatography.
In using a calcium phosphate-based compound as a biomaterial, a powder of calcium phosphate-based compound is prepared from a slurry containing the calcium phosphate-based compound. The prepared powder is formed into a desired shape to obtain a green body, and it is then sintered. The thus obtained sintered body is used for artificial bones, dental implants and the like in the medical and dental fields.
In using a calcium phosphate-based compound as a stationary phase material for chromatography, a calcium phosphate-based compound powder is prepared in the same manner as in the case for a biomaterial. The thus prepared powder is sintered, and the sintered powder is used as a stationary phase to be filled in a column or the like for chromatography.
A problem exists, however, with such a sintered body for use in artificial bones, dental implants, and the like in that processing and control of porosity are difficult to carry out if the prepared powder does not have sufficient (uniform) particle strength. Generally, such a sintered body is manufactured through the following three steps. Firstly, a prepared powder is pre-sintered and then ground using a grinder. Secondly, the ground powder is mixed with, for example, an aqueous solution of methylcellulose. Thirdly, the mixture is gelled to be formed into a block shape. The grinding of the pre-sintered powder in the first step is necessary for properly giving irregularities on the surface of each particle of the ground powder so that each particle can have an increased surface area, thereby increasing contact area between the particles. A sintered body manufactured from such a powder of which particles have increased surface area exhibits excellent mechanical strength. However, if the particle strength of the prepared powder (that is a powder prior to pre-sintering) is too low, the pre-sintered powder is excessively fragmented to become too fine particles when ground. On the other hand, if the particle strength of the prepared powder is too high, such an effect due to grinding as described above can not be obtained so that the ground powder will not have a uniform particle size distribution, and thus a sintered body manufactured from such a powder can not have uniform porosity and strength.
A problem also exists with a sintered powder for use as a stationary phase for chromatography in that if a powder prepared prior to sintering does not have sufficient particle strength, the sintered powder will tend to collapse when filled in a column, which may result in clogging of a filter. One outcome of this problem is that proper separation of proteins can not be carried out.